Structural properties in relation to oral enzymatic digestibility of starch gels based on pure starch components and high amylose content

The structure of different starch gels made of native high-amylose maize starch, purified amylose polymers and waxy-maize starch was studied using dynamic viscoelastic measurements. In this study starch gels with high-amylose content had the most rigid structure followed by pure amylose and amylopectin gels. The addition of a high amount of maltitol to the high-amylose starch dispersion before heating reduced the formation of networks. The enzymatic digestibility of various starch gels was measured using both in vitro and in vivo methods. In 5 min alpha-amylase hydrolysis, the extent of degradation was decreased when the amylose concentration was increased in the amylose network and when maltitol syrup was added. Acid production from starch gels was followed in vivo by monitoring pH changes in approximal plaque. The correlation between minimum plaque pH and the extent of hydrolysis determined in vitro was relatively good. The amount of amylose in the network was not the factor that affected the extent of short-term oral enzymatic degradation. The more rigid the gel, the lower the extent of hydrolysis. However, even though high-amylose starch gels with a rigid structure were hydrolysed to a minor extent in salivary alpha-amylase hydrolysis in vitro they did not induce any pH changes in human plaque.